Ground Fault Circuit Interrupter

Thread Starter

moonlystar1111

Joined Feb 1, 2024
57
Can anyone please explain what is happening in this circuit diagram. I'm new in analog circuit Designing and want to simulate this circuit.
Also is this schematic enough for me to simulate
 

LowQCab

Joined Nov 6, 2012
4,075
It's somewhere between "very difficult" and "totally impossible" to accurately simulate a GFI Circuit.

In an actual physical application, just purchasing the required Special-Transformers will cost You
much-much more than simply buying a standard GFI-Outlet,
or a GFI-Circuit-Breaker, at a nearby Hardware-Store.

If You just want to know how it works .............
It monitors for any Current-Flow differences between the Hot and Neutral Wires.
Any difference in Current-Flow indicates that the Current must be
going somewhere that it's not supposed to go, and that's a dangerous situation.
.
.
.
 

Thread Starter

moonlystar1111

Joined Feb 1, 2024
57
Then good luck with that.
It's rather like taking Quantum Physics as your first physics course.
I'm an electronics engineer for your information and this is my project on which I'm working on. Im new to analog designing doesn't mean I was born yesterday and want to simulate circuits today. I have worked on micro controllers previously but going deeper into analog is a new thing for me.
 

Thread Starter

moonlystar1111

Joined Feb 1, 2024
57
It's somewhere between "very difficult" and "totally impossible" to accurately simulate a GFI Circuit.

In an actual physical application, just purchasing the required Special-Transformers will cost You
much-much more than simply buying a standard GFI-Outlet,
or a GFI-Circuit-Breaker, at a nearby Hardware-Store.

If You just want to know how it works .............
It monitors for any Current-Flow differences between the Hot and Neutral Wires.
Any difference in Current-Flow indicates that the Current must be
going somewhere that it's not supposed to go, and that's a dangerous situation.
.
.
.
I'm half done with the simulation but when i combine different parts/blocks of circuit, it is not working. Like some part of the circuit needs grounding capacitor, filter circuit, current limiting resistor, or need of increasing amplitude of signal etc. And im not able to do that. That's why I want to know if this schematic is enough for simulation or its just me who is not getting it.
 

crutschow

Joined Mar 14, 2008
34,454
I want to know if this schematic is enough for simulation or its just me.
Simulating the innards of an IC can be difficult, since they usually don't show the complete circuit, only a basic block diagram.
As to why your circuit won't simulate, that's anyone's guess.
What you are trying to do is rather like analyzing a microprocessor's operation as your first digital problem.
How much analog training have you had?
 

Thread Starter

moonlystar1111

Joined Feb 1, 2024
57
Simulating the innards of an IC can be difficult, since they usually don't show the complete circuit, only a basic block diagram.
As to why your circuit won't simulate, that's anyone's guess.
What you are trying to do is rather like analyzing a microprocessor's operation as your first digital problem.
How much analog training have you had?
I have studied about op amp, comparator, transistors (FETs BJTs their types), logic gates( ttl, rtl, cmos), instrument amplifier, oscillator, 555 timer, gain stability bandwidth, power amplifier, filter circuit etc
But i haven't done spice simulation before using this.
 

LowQCab

Joined Nov 6, 2012
4,075
It is extremely difficult, or even impossible, to simulate all of the various nuances of a particular Transformer,
especially when we are talking about accurately measuring single-digit milliamps of Current.

The complexity of the Software-Model would be
almost completely impractical for everyday usage by us mere mortals.

The Transformers that have been specially designed to work with the particular Chip and Circuitry
that has been previously referred to, are called-out by the exact manufacturers part-number.
There are most likely no compatible Software-Models available for common simulation programs,
at least none that are available to the general-public.

You can probably try to create a generic Transformer-Model with a dual-Secondary,
with the Secondaries set up out of Phase similar to a Common-Mode-Choke configuration,
and, with a ~2000 to 1 turns-ratio.
This would give You something to "play with",
that is, if You can get it to work.

If You do get it to "work", it will work in theory only.
Actual Real-World performance will be a total crap-shoot.
.
.
.
 

MisterBill2

Joined Jan 23, 2018
18,535
For simulation, the comments are correct. A GFCI is a deceptively complex device. Also, the circuit for the three wire outlet is rather baffling to me. I must be based on some part of the explanation that I did not see.
And really, the explanation on page 4 of the data set is as good as it will get.
 

michael8

Joined Jan 11, 2015
415
If You just want to know how it works .............
It monitors for any Current-Flow differences between the Hot and Neutral Wires.
Any difference in Current-Flow indicates that the Current must be
going somewhere that it's not supposed to go, and that's a dangerous situation.


Depending on which circuit in the datasheet you are simulating, it does more than that.

The data sheet says:

the RV4145A can detect and protect against both hot−wire− to−ground and neutral−wire−to−ground faults.

I suspect it can detect a neutral to ground fault in something plugged in which isn't switched on.
How does it do that? That it takes 2 transformers is a clue.

Post your ltspice simulation file of what you have so far. And say which circuit you are simulating...
 

Ya’akov

Joined Jan 27, 2019
9,167
I'm half done with the simulation but when i combine different parts/blocks of circuit, it is not working. Like some part of the circuit needs grounding capacitor, filter circuit, current limiting resistor, or need of increasing amplitude of signal etc. And im not able to do that. That's why I want to know if this schematic is enough for simulation or its just me who is not getting it.
Welcome to AAC.

With no intention of insulting or diminishing your abilities, I think you‘ve made a classic mistake akin to changing more than one condition while trying to troubleshoot.

You are trying to learn analog circuits and simulations at the same time. Since you are a neophyte concerning both, you can’t know which of them is the source of the trouble you are having. It would probably serve you well to choose some sub-circuits from the GFCI to cut your teeth on the simulations.

Pick some simple portions of the GFCI’s construction that offer circuits more easily reduced to simulations—then simulate those to learn more about both the essential behavior of that circuit and the process of simulating circuits.

Build up to the more complex interactions embodied in the entire GFCI and you will have a much better chance of knowing where the limits lie: in the schematic, in the simulation, or in your current knowledge.

Good luck.
 

MisterBill2

Joined Jan 23, 2018
18,535
In addition to the other challenges it is not likely that the spice simulator has any accurate models for the portions of that IC device. In addition, it is even less likely that other manufacturers of GFCI devices would be willing to share thier hard-learned insights with a would-be competitor. So an accurate simulation is rather unlikely.
Besides all of that, it is not reasonable to expect that a simulator can produce an accurate simulation of this circuit.
 

Alec_t

Joined Sep 17, 2013
14,318
You could certainly simulate the function of the circuit in Fig.1 of the post #1 attached pdf, albeit with some limitations and assumptions.
 

Cairmot

Joined Feb 4, 2024
1
Complete simulations are only useful if you can accurately model all the parts. As has been mentioned it can be quite difficult to get those models, especially for the transformer. To start, I'd suggest you focus on figure 4 (and PRINCIPLES OF OPERATION), assume ideal performance from the transformer, and assume the IC is an opamp, and neglect the SCR circuit. This would allow you to get an understanding of the circuit operation.

An important (conceptual) distinction is to consider the operation as not so much measuring the current differences, but seeing how well the currents balance. If both currents are the same, the magnetic fields will cancel and no voltage will be developed on the output winding. Imperfections in the transformer cause this not to be 100% true, but apparently it's close enough so that the device performs its desired function.

Once this circuit is set up you can then start adding details. Replace The Ideal OP amp with one you have constructed from the circuit diagram, add the SCR. Shunt some current, from one of the wires around the transformer, i.e. a ground fault, and see what happens.


This should give you a good understanding of the circuit. Be sure to compare your simulations with reality as much as possible to help validate your model.

Cairmot
 

MisterBill2

Joined Jan 23, 2018
18,535
Reading posts #6 and #7, this may be a design engineer who has been assigned to creat a new product that avoids the patents of all the others and is cheaper to build so that the price can be competitive. Been there done that and won the prize.
What would be new is a GFID that can survive a breaker tripping short circuit on the load side. There are at least three brands that while they provide the required safety very well, they can not survive that short circuit event. So that leaves the door open for some brilliant design that can survive the dead-short fault. THAT would be a product that nobody offers yet.
 

michael8

Joined Jan 11, 2015
415
a GFID that can survive a breaker tripping short circuit on the load side

What's the problem with that? I could see either damage to the contacts as they open during the short
or high voltages on the output of the coupling transformers in the GFID damaging the IC.
Or some sort of permanent saturation of the magnetics in the GFID?
 

MisterBill2

Joined Jan 23, 2018
18,535
a GFID that can survive a breaker tripping short circuit on the load side

What's the problem with that? I could see either damage to the contacts as they open during the short
or high voltages on the output of the coupling transformers in the GFID damaging the IC.
Or some sort of permanent saturation of the magnetics in the GFID?
I have three of them that were destroyed by an accidental line to either neutral or ground short. The loud, breaker poping kind of short. The contacts were not damaged because they did not have time to open, or even start opening.
 

michael8

Joined Jan 11, 2015
415
What's the damage to the GFID if it's not the contacts? I assume they didn't work, what did they do or not do:
a. not reset from trip?, b. never trip again?, c. look like charcoal?

Did the insides look ok but the GFID not work (what I'd expect for IC damage).
 
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